Pipeline tools, such as that disclosed in U.S. Pat. No. 6,917,176, operate using an on-board power source that supplies power to subsystems used by the tool. For example, power may be needed for propelling the pipeline tool through a pipeline, operating measurement and sensor devices such as light sources and cameras, and energizing control and communications circuitry. Pipeline tools commonly include a rechargeable power source and a charging contact for on-board energy needs. The entire aforementioned U.S. Pat. No. 6,917,176 is incorporated herein by reference for its disclosure of a pipeline tool having a rechargeable power source and a charging contact. Pipeline tools may be used in both pressurized and non-pressurized pipelines used to transport a variety of fluids in both liquid and gas forms.
Charging a rechargeable power source of a pipeline tool used within a pressurized pipeline presents a challenge because opening the pipeline will require depressurization of the pipeline and the downtime, cost, and environmental concerns associated therewith. Charging a rechargeable power source of a pipeline tool used within a pressurized natural gas pipeline presents a special challenge because safety regulations prohibit the flow of power across a pressure barrier associated with the natural gas pipeline. One approach for dealing with these challenges is to return the pipeline tool to its original deployment location and remove the pipeline tool from within the pressurized pipeline for recharging. After the tool's power source has been recharged, it is again inserted into the pipeline and deployed for further service. This approach is time consuming because the pipeline tool may need to retrace its path in the pipeline. Energy spent returning the pipeline tool to the deployment location is not available to run the intended service functions of the tool. This approach is also limiting in terms of the range of pipeline distance coverable from a given deployment location, and thus requires creation of a relatively large number of deployment locations along the pipeline.
Apart from the special challenge posed by natural gas pipelines, there is a need for a charging power source that is easily portable over large pipeline distances. The need for portability combines with the special regulatory challenge described above when dealing with natural gas pipelines, so that providing the charging power source within the pressure barrier must also be achieved. Batteries are one option for use as a charging power source, however they are costly and have a limited charge life.